High-Performance Perovskite Solar Cells Using Iodine as Effective Dopant for Spiro-OMeTAD

The p-type dopant of spiro-OMeTAD has been identified as a rational strategy for the enhancement of the hole transport ability in perovskite solar cells (PSCs). Herein, to enhance the conductivity and hole-extraction ability of spiro-OMeTAD, a low-cost and facile method is developed by introducing iodine into the hole transport materials. Morphology observation, energy gap characterization, and photoelectrochemical measurements indicate that as a mild Lewis acid, oxidant, and p-type dopant, iodine moderately oxidizes spiro-OMeTAD, optimizes the energy match with perovskite, mitigates the trap state density, interface resistance, and carrier recombination, and improves the hole-extraction ability and carrier transport capacity. Consequently, a planar PSC based on the spiro-OMeTAD doped with 8 wt% iodine achieves a champion power conversion efficiency (PCE) of 19.69%. Conversely, the device with pristine spiro-OMeTAD gets an efficiency of 18.04%. This work indicates a potential application of iodine as a promising p-type dopant for spiro-OMeTAD in PSCs.